Thanks, but I already know it, and what's more, now the train is free for us, since we're travelling from Hungary (a new destination for ryanair). Anyway, is it enough to show it to the conductor? (I read that there is a place at the airport where I should get the vochures first)
Yes, it seems you have to go to the airport information desk to collect a voucher. You'll get this by showing them your original booking confirmation.
Information